FBI Responds to Science Issues in Anthrax Case

During a recent American Society for Microbiology Biodefense (ASMBD) meeting in Baltimore , Maryland , questions were raised regarding two scientific analyses conducted during the course of the anthrax investigation. While this information is not new, it is important for the FBI to clarify the science since these findings continue to be misinterpreted by various media outlets.

The first item involves the elemental analysis of the anthrax spores that was conducted by Dr. Joseph Michael, a materials scientist at Sandia National Laboratories. At the conference, Dr. Michael presented analyses of three anthrax letters (Leahy, Daschle, and New York Post). He concluded that the anthrax powder in the three letters shared a chemical fingerprint but did not match the chemical fingerprint of spores in Ivins’ flask. Spores from the letters showed a distinct chemical signature that included silicon, oxygen, iron, tin, and other elements. Spores from Ivins’ RMR-1029 flask did not contain those elements in quantities that matched the letter spores. This is not unusual considering that Ivins’ RMR-1029 preparation had been submerged in water and other chemicals since 1997 and was a mixture of 34 different spore preparations. The letter spores were dried spores, produced from two separate growth preparations as indicated by differences in the New York and Washington, D.C. mailings. Although the chemical fingerprint of the spores is interesting, given the variability involved in the growth process, it was not relevant to the investigation.

It is important to note that the genetic profile of the spores from the letters and the spores from Ivins’ RMR-1029 flask was identical. Ivins’ RMR-1029 spore preparation had the same combination of anthrax mutations found in the letters. Only eight of the anthrax samples collected during the course of the investigation matched the genetic profile in the letter material and all were linked back to RMR-1029. This conclusion was the most significant and relevant scientific finding in the case.

By analogy, if one were to grow a corn stalk from a specific corn seed, the trace chemical fingerprint of the stalk might differ from that of the seed due to different compositions—for example iron—in the respective fertilizers used to grow each; however, the genetic profile of the seed and the stalk would be identical.

The second item involves isotopic analysis of the mailed anthrax. Media reports indicated that FBI scientists had concluded in 2004 that out of many domestic and foreign water samples analyzed only water from near Fort Detrick, Maryland, where Dr. Ivins worked, had the same isotopic signature as the water used to grow the mailed anthrax. This statement is incorrect. While water isotopic analysis was researched, the FBI concluded that there were too many confounding variables to precisely match bacteria that were grown using different materials and recipes. This technique was not relevant to the investigation.

While we have full confidence in our scientific approach, an additional independent review will provide further validation and thus benefit the larger scientific community. Consideration of an outside review began before any public disclosure of the scientific aspects of the investigation. This follows our approach throughout the investigation: to bring in external scientists to review and provide advise on our methodologies.